Danielli Alberto, Romagnoli Simona, Roncarati Davide, Costantino Lorenzo, Delany Isabel, Scarlato Vincenzo
Department of Biology, University of Bologna, Via Selmi 3, 40126 Bologna, Italy.
J Bacteriol. 2009 Jun;191(11):3717-25. doi: 10.1128/JB.01741-08. Epub 2009 Apr 3.
Balancing metal uptake is essential for maintaining a proper intracellular metal concentration. Here, we report the transcriptional control exerted by the two metal-responsive regulators of Helicobacter pylori, Fur (iron-dependent ferric uptake regulator) and NikR (nickel-responsive regulator), on the three copies of the fecA genes present in this species. By monitoring the patterns of transcription throughout growth and in response to nickel, iron, and a metal chelator, we found that the expression of the three fecA genes is temporally regulated, responds to metals in different ways, and is selectively controlled by either one of the two regulators. fecA1 is expressed at a constant level throughout growth, and its expression is iron sensitive; the expression of fecA2 is mainly off, with minor expression coming up in late exponential phase. In contrast, the expression of fecA3 is maximal in early exponential phase, gradually decreases with time, and is repressed by nickel. The direct roles of Fur and NikR were studied both in vitro, by mapping the binding sites of each regulator on the promoter regions via DNase I footprinting analysis, and in vivo, by using primer extension analyses of the fecA transcripts in fur and nikR deletion strains. Overall, the results show that the expression of each fecA gene is finely tuned in response to metal availability, as well as during the bacterial growth phase, suggesting specific and dedicated functions for the three distinct FecA homologues.
平衡金属摄取对于维持适当的细胞内金属浓度至关重要。在此，我们报告了幽门螺杆菌的两种金属响应调节因子Fur（铁依赖性铁摄取调节因子）和NikR（镍响应调节因子）对该物种中存在的三个fecA基因拷贝所施加的转录控制。通过监测整个生长过程以及对镍、铁和金属螯合剂的反应中的转录模式，我们发现三个fecA基因的表达受到时间调控，对金属有不同的反应方式，并由这两种调节因子中的任何一种选择性控制。fecA1在整个生长过程中以恒定水平表达，其表达对铁敏感；fecA2的表达主要处于关闭状态，在指数后期有少量表达。相比之下，fecA3的表达在指数早期最高，随时间逐渐降低，并受到镍的抑制。通过DNase I足迹分析绘制每个调节因子在启动子区域的结合位点，在体外研究了Fur和NikR的直接作用，并通过对fur和nikR缺失菌株中fecA转录本进行引物延伸分析，在体内进行了研究。总体而言，结果表明每个fecA基因的表达会根据金属可用性以及细菌生长阶段进行精细调节，这表明三种不同的FecA同源物具有特定且专门的功能。
